Treatment for acute kidney failure and chronic end stage renal disease is accomplished by various forms of continuous ambulatory peritoneal dialysis and hemodialysis, presently the most commonly used form of therapy. In all current hemodialysis procedures, blood is periodically removed from the patient""s body, dialyzed ex-vivo and the treated blood returned to the body. Single patient conventional hemodialysis procedures are performed at an out-patient center 2 or 3 times a week in 3 to 4 hour sessions during which the patient""s blood toxins are removed by dialysis and filtration to eliminate the toxins generated by the body during the 3 or 4 day period preceding the hemodialysis, and during the time the treatment is carried out. Thus, unlike normal kidney function in which dialysis is carried out continuously, the hemodialysis creates non-uniform toxin removal with xe2x80x9cpeaks and valleysxe2x80x9d of toxin concentrations. Moreover, during the time that the toxins are above normal, the patient feels ill and the consequent buildup of fluid volume in the body caused by lack of urination results in a severe volume load on the right heart stressing an already compromised cardiovascular system, as well as creating an imbalance in the electrolyte system of the blood. During the hemodialysis, blood is pumped from the body and through a dialyzer cartridge at a high flow rate and simultaneously fluid is removed from the blood by ultrafiltration to reduce the blood volume to normality. The resulting procedure causes a massive change in blood hemodynamics in a short period of time and produces additional heavy stress on the human system with severe fluctuations in blood pressure and trauma to other body organs. Yet another serious problem is the persistent and periodic clotting of the blood in the inner lumens of the dialyzer even though the patient is anti-coagulated with drugs such as heparin. The aforesaid current hemodialysis procedures are performed on over 600,000 patients per year in the United States alone at an expense to the healthcare system of over twelve billion dollars per year.
In U.S. Pat. Nos. 4,590,224, 5,151,082, 5,152,743, 5,224,926 and 5,735,809 there are disclosed methods and apparatus for in vivo separation of plasma from blood utilizing one or more hollow elongated microporous fibers implanted within a patient""s blood vessel. The fibers are made of a microporous polymeric fiber membrane material having a pore size sufficient to allow diffusion of plasma into the hollow fiber interior but preventing cellular components larger than plasma to diffuse, ultrafiltrate or enter the fiber interior. The fiber or fibers are implanted within the blood vessel without significantly obstructing fluid flow through the vessel while providing the aforesaid in vivo plasma separation. The fiber assembly is secured in fluid communication with a catheter, preferably a dual lumen catheter having a first tube permitting plasma passage from the fiber and a second tube for returning plasma to the blood vessel after treatment. Various configurations and methods of fabrication as well as materials having a variety of characteristics and performance abilities are disclosed in the aforesaid patents and application as are various systems, apparatus, components and methods for use including measurement of blood parameters, kidney dialysis, and separation and removal of a substantial number of specific materials and plasma components, the descriptions of which are incorporated herein by reference. By continuously extracting plasma from the blood in-vivo and dialyzing only the plasma ex-vivo eliminates many of the failings of the present hemodialysis systems and procedures.
The present invention is intended to provide further improvement in removing toxins from a patient""s blood. In the present invention, all of the function of kidney dialysis therapy can be performed continuously in-vivo and in-situ without removing from the body any blood, plasma or blood components except the toxins and other undesirable elements to be eliminated, thus substantially emulating the natural kidney.
In the present invention, a filter device comprising a dialysis membrane is implanted within the superior vena cava. The filter device includes a dialysate cavity which is exposed to the interior surface of the dialysis membrane, with the exterior dialysis membrane surface exposed to the patient""s blood within the blood vessel. The filter device is secured at the end of a multiple lumen catheter through which dialysate fluid is continually directed. Conventional dialysate fluid, comprising sterilized water and desirable amounts of electrolytes and /or osmotic materials, well known to those skilled in the art, may be used. The dialysate fluid passing into the dialysate cavity of the filter device is in direct diffusive communication with the patient""s blood to perform the dialysis function, and the resulting toxin-contaminated dialysate is removed from the filter device through a second catheter lumen. The filter device may also include an ultrafiltration cavity whereby the dialysate is in direct convective communication with the blood to produce an ultrafiltration function. Using such a device results in the blood and plasma dialyzed in place, and excess fluids extracted within the body whereby neither blood nor plasma need be removed from the patient""s body. The invention also includes apparatus and systems as well as different configurations and embodiments of filter devices used in the process of the invention. Such methods and apparatus as well as the advantages will be disclosed in the following detailed description.